Effect of SBR/BR elastomer blend ratio on filler and vulcanization characteristics of silica filled tire tread compounds

Abstract The effect of the SBR/BR blend ratio on marching modulus – no-plateau torque profile in vulcametry – of a silica filled tire tread compound is investigated. This is a tedious recurring problem, as it precludes the establishment of optimal vulcanization conditions. It was expected that the elastomer characteristics, SBR and BR in this study, and their physical affinity towards silica will influence the degree of silica dispersion and flocculation, thus the curing kinetics and marching modulus. Within this study, a wide series of properties related to dispersion and curing was measured depending on the polymer ratio, with the final goal to elaborate the contribution of the SBR/BR ratio to the marching modulus, as a means to suppress this phenomenon. The SBR/BR ratio indeed does influence the vulcanization characteristics of silica compounds; in particular the tendency to marching modulus. This effect stems from the specific characteristics of the polymers, mainly their interaction with silica and crosslinking reactivity. This was concluded based on the correlations found between the Marching Modulus Index (MMI) and the polymer ratio, as well as filler flocculation rate (FFR) and polymer-filler coupling rate (CR). A model explaining the different trends of MMI and FFR in the SBR-rich and BR-rich compounds is proposed.